The present invention relates to intraocular lenses (IOLs). More particularly, the present invention relates to IOLs which are adapted to provide accommodating movement in the eye.
The human visual system includes the eyes, the extraocular muscles which control eye position within the eye socket, the optic and other nerves that connect the eyes to the brain, and particular areas of the brain that are in neural communication with the eyes. The visual system is particularly well adapted for the rapid and precise extraction of spatial information from a field of view which is accomplished by analyzing the continuously changing patterns of radiant flux impinging upon the surfaces of the eyes.
Image formation is greatly complicated by the movement of the eyes within the head, as well as by the movement of both eyes and the head relative to the external sea of radiant energy. Visual input is ordinarily sampled by discrete momentary pauses of the eyes called fixations, interrupted by very rapid ballistic motions known as saccades which bring the eye from one fixation position to the next. Smooth movements of the eyes can occur when an object having a predictable motion is available to be followed.
Each eye forms an image upon a vast array of light sensitive photoreceptors of the retina. The cornea is the primary refracting surface which admits light through the anterior part of the outer surface of the eye. The iris contains muscles which alter the size of the entrance port of the eye, or pupil. The crystalline lens has a variable shape, under the indirect control of the ciliary muscle. Having a refractive index higher than the surrounding media, the crystalline lens gives the eye a variable focal length, allowing accommodation to objects at varying distances from the eye.
Much of the remainder of the eye is filled with fluids and materials under pressure which help the eye maintain its shape. For example, the aqueous humor fills the anterior chamber between the cornea and the iris, and the vitreous humor fills the majority of the volume of the eye in the vitreous chamber. The crystalline lens is contained within a third chamber of the eye, the posterior chamber, which is positioned between the anterior and vitreous chambers.
The human eye is susceptible to a score or more of disorders and diseases, a number of which attack the crystalline lens. For example, cataracts mar vision through cloudy or opaque discoloration of the lens of the eye. Cataracts often result in partial or complete blindness. If this is the case, the crystalline lens can be removed and replace with an intraocular lens, or IOL.
While restoring vision, conventional IOLs have limited ability for accommodation (i.e., the focusing on near objects). This condition is known as presbyopia. To overcome presbyopia of an IOL, a patient may be prescribed eyeglasses. Alternative attempts in the art to overcome presbyopia focus on providing IOLs with accommodation ability. Accommodation may be accomplished by either changing the shape of the IOL, e.g., to become more convex to focus on near objects, or by moving the IOL along its optical axis. For example, a number of these approaches bias an IOL to be located in the most posterior position of the posterior chamber of the eye under rest conditions. When near focus is required, the ciliary muscle contracts, and the IOL moves forwardly, which is known as positive accommodation. In the absence of ciliary muscle contraction, the IOL is biased rearwardly to the most posterior position. While these approaches may provide limited accommodation, the posterior bias and the configuration of the IOL prevent sufficient forward axial movement required for full-range accommodation.
In view of the foregoing, it would be beneficial in the art to provide IOLs adapted for sufficient accommodation to reduce significantly or to overcome the effects of presbyopia.
New intraocular lenses (IOLs) effective to provide accommodation have been discovered. The present IOLs provide effective accommodation using one or more optics. The IOLs of the invention also inhibit cell growth, particularly epithelial cell growth, onto the optics of the IOLs. The IOLs of the present invention are configured, and preferably promote cellular and fibrous growth to desired regions of the IOL, to increase the amount of force exerted by the eye against the IOLs to increase the amount of accommodation achieved. The present IOLs are relatively straightforward in design, can be produced using conventional IOL manufacturing procedures and can be inserted or implanted in eyes, e.g., human eyes, using surgical techniques which are the same as or analogous to such techniques used with conventional IOLs.
According to one aspect of the invention, an intraocular lens is provided which includes an optic for focusing light on a retina and a movement assembly coupled to the optic. The movement assembly is adapted to cooperate with the eye to effect accommodating movement of the optic. The movement assembly includes a movement member with a proximal region coupled to the optic. The movement member, and in particular the proximal region of the movement member, extends radially outwardly from the optic and includes an enlarged distal region with a contact surface adapted to be in contact with a peripheral region of a capsular bag of an eye.
One of the advantages of the present invention is that the IOL is held within, preferably attached to, the capsular bag. More specifically, the contact surface of the enlarged distal region may have an axial length of at least about 1 mm. Therefore, depending upon the radius of the IOL, the contact surface has a relatively large surface area with which to contact the capsular bag.
The contact of the IOL with the capsular bag is further enhanced by disposing the enlarged distal region in an angled manner relative to the proximal region of the member. Preferably, the contact surface is substantially parallel to the optical axis of the IOL. The relatively large contact surface is effective in maintaining the position of the IOL particularly directly following implantation and, on a long term basis, is effective in increasing the amount of accommodation provided by the IOL.
The relatively large surface area of the contact surface also promotes cellular and fibrous growth to or onto this region of the IOL, which further holds and retains the IOL within the capsular bag and increases the amount of force that may be exerted through the capsular bag onto the IOL to provide accommodation, as desired. Post-operative cellular and fibrous growth of the interior of the capsular bag to the enlarged distal region of the movement assembly may, and preferably does, enable the IOLs of the present invention to function substantially analogous to a natural crystalline lens.
To further facilitate this post-operative cellular growth, the enlarged distal region may include a plurality of depressions or through holes. Each of the through holes preferably provides increased growth of cells and fibrin onto the enlarged distal region or regions of the IOL. Accordingly, the IOL is very effectively attachable, preferably substantially permanently attachable, to the capsular bag. This attachment of the IOL to the capsular bag facilitates the axial movement of the IOL in direct response to changes in the capsular bag, therefore providing effective accommodation, analogous to a natural crystalline lens.
The IOLs of the present invention preferably inhibit unwanted posterior capsule opacification (PCO) of the optic. Thus, the distal region or regions of the movement assembly preferably is or are joined to the proximal region or regions so that one or more sharp edges, that is preferably edges which occur at discontinuities (rather than at smooth, continuous transitions) when viewed by the naked human eye, are present between the joined proximal and distal regions. Such sharp edges have been found to advantageously inhibit PCO by inhibiting the growth of cells, for example, epithelial cells, from the capsular bag onto the optic of the present IOLs.
To further enhance the accommodating movement of the present IOLs in cooperation with the eye, the movement assembly preferably is positioned relative to the optic so that, with the IOL at rest, that is with no forces acting on the IOL to effect accommodation, the proximal region of the movement member is positioned at an angle other than 90xc2x0 relative to the central optical axis of the optic. In a very useful embodiment, the optic, in the rest position as noted above, is anteriorly vaulted. Also, the movement member or members preferably include a hinge, or a plurality of hinges, located on the proximal region or regions of the movement members, more preferably closer to the optic than to the distal region or regions. Each of these features, either individually or any combination thereof, is effective to further facilitate the movement of the optic to provide the desired amount of accommodation.
According to another aspect of the invention, the movement assembly includes a plurality of movement members, preferably spaced apart, for example, radially or circumferentially spaced apart, from each other. Each movement member includes a proximal region coupled to the optic and an enlarged distal region, for example, as described elsewhere herein. The enlarged distal regions each have a contact surface adapted to be in contact with a peripheral region of a capsular bag of an eye. In addition, the enlarged distal regions may be configured such that the contact surfaces are substantially coaxial with the optical axis of the optic.
A plurality of spacer or cut-out regions preferably are located between radially or circumferentially adjacent movement members. Such cut-out regions are effective to prevent buckling of the IOL during accommodating movement in the eye. Such spacers or cut-out regions may be open. In one useful embodiment each of such regions is at least partially covered with or by a structural material having increased flexibility relative to the movement members. Thus, the IOL is prevented from buckling while, at the same time the structural material is effective to at least inhibit cell growth from the capsular bag onto the optic. This structural material may have the same chemical make-up as the proximal regions of the movement members and have a reduced thickness relative to the proximal regions to provide the increased flexibility.
Another advantage of the present IOLs is that a second optic may be provided. According to this multi-optic embodiment, the secondary optic may be coupled to the enlarged distal region or regions with one or more secondary movement members.
In one useful embodiment, the enlarged distal region or regions of the movement member or members are provided with a groove or grooves. The secondary movement member or members are adapted to fit into the groove or grooves, thereby holding the second optic in position in the eye. Alternately, the second optic and secondary movement members may be formed integrally with the optic/movement assembly combination.
In a further useful embodiment of present invention, the enlarged distal region or regions of the movement member or members are mechanically coupled to the perspective proximal regions. In one particular embodiment, an intraocular lens comprises a plurality of arcuate segments mechanically coupled (e.g., adhered) to an integrally formed optic and radially outward movement members. The arcuate segments may have one or more grooves for receiving one or more movement members, thus forming either a one-optic or a two-optic system.
The second optic preferably has an optical power, or even substantially no optical power. The combination of the optic and second optic together preferably provides the optical power required or desired by the patient in whose eye the IOL is to be implanted. For example, the second optic can have a plano or substantially plano optical power or a relatively highly negative optical power, for example, between about xe2x88x9230 diopters to about xe2x88x9210 diopters, as desired. The second optic preferably is located posterior of the optic. In one useful embodiment, the second optic, in the eye, is substantially maintained in contact with the inner posterior wall of the capsular bag. This feature inhibits or reduces the risk of cell growth or migration from the capsular bag into the second optic. The second optic in such a posterior position often has only a relatively restricted, if any, amount of axial movement. Such a posterior second optic preferably is posteriorly vaulted, with the IOL in the rest position as described elsewhere herein, to facilitate maintaining the posterior face of the second optic in contact with the inner posterior face of the capsular bag.
Any and all of the features described herein and combinations of such features are included within the scope of the present invention provided that the features of any such combination are not mutually inconsistent.